# -*- coding: utf-8 -*-
# ITP1_10_A

import math

pos = list(map(float, input().split()))
x = abs(pos[2] - pos[0])
y = abs(pos[3] - pos[1])

print(math.sqrt(x**2 + y**2))
 import math math pos = list(map(float, input().split())) pos list(map(float, input().split())) list map(float, input().split()) map float input().split() ().split () input split x = abs(pos[2] - pos[0]) x abs(pos[2] - pos[0]) abs pos[2] - pos[0] pos[2] pos 2 pos[0] pos 0 y = abs(pos[3] - pos[1]) y abs(pos[3] - pos[1]) abs pos[3] - pos[1] pos[3] pos 3 pos[1] pos 1 print(math.sqrt(x**2 + y**2)) print math.sqrt(x**2 + y**2) math.sqrt math sqrt x**2 + y**2 x**2 x 2 y**2 y 2 y = abs(pos[3] - pos[1]) abs(pos[3] - pos[1]) y pos = list(map(float, input().split())) list(map(float, input().split())) pos x = abs(pos[2] - pos[0]) abs(pos[2] - pos[0]) x
# -*- coding: utf-8 -*-
# ITP1_10_A

import math

pos = list(map(float, input().split()))
x = abs(pos[2] - pos[0])
y = abs(pos[3] - pos[1])

print(math.sqrt(x**2 + y**2))

